How to adjust audio balance (left or right speaker) in Logic 9?

Hi,

I am playing a midi file with several instruments in Logic. Some of the instruments seem to output from the left speaker only, while others are from the right speaker only.

In each instrument there is a small circular graphic with a number (its either -50 or +50 depending on the instrument). It seems that changing this value adjusts the balance:

ie. -50 = left speaker only

+50 = right speaker only

0 = Both speakers equally.

After I change the values to 0, the audio plays through both speakers (this is what I want). But the moment I rewind the midi file, all instruments go back to their previous values of -50 or + 50. How do I make sure that the settings remain the way I want, and don't go back to what they were when I rewind?

Thanks.